Understanding recent changes in suicide rates among the middle-aged: period or cohort effects?

We examined trends in suicide rates for U.S. residents aged 40 to 59 years from 1979 to 2005 and explored alternative explanations for the notable increase in such deaths from 1999 to 2005.

We obtained information on suicide deaths from the National Center for Health Statistics and population data from the U.S. Census Bureau. Age- and gender-specific suicide rates were computed and trends therein analyzed using linear regression techniques.

Following a period of stability or decline, suicide rates have climbed since 1988 for males aged 40-49 years, and since 1999 for females aged 40-59 years and males aged 50-59 years. A crossover in rates for 40- to 49-year-old vs. 50- to 59-year-old males and females occurred in the early 1990s, and the younger groups now have higher suicide rates. The post-1999 increase has been particularly dramatic for those who are unmarried and those without a college degree.

The timing of the post-1999 increase coincides with the complete replacement of the U.S. population's middle-age strata by the postwar baby boom cohorts, whose youngest members turned 40 years of age by 2005. These cohorts, born between 1945 and 1964, also had notably high suicide rates during their adolescent years. Cohort replacement may explain the crossover in rates among the younger and older middle-aged groups. However, there is evidence for a period effect operating between 1999 and 2005, one that was apparently specific to less-protected members of the baby boom cohort.